Air Products will use Salesforce.com’s hosted software applications across its sales and marketing divisions.

The financial worth of the deal to Salesforce.com is not clear. But it will certainly boost the company’s subscriber numbers, proving to skeptical rivals like Siebel Systems Inc that its hosted ASP model can scale-up to large deployments.

Investors in ASP firms tend to gauge corporate performance from the number of subscribers signed up. Salesforce.com has been adding them consistently. Earlier this month the San Francisco-based company said it added over 41,000 paying subscribers, including 1,400 new customers, in its last fiscal quarter.

Overall the company has nearly 17,000 customers and a subscriber base of 310,000 users.

Salesforce.com continues to pressure traditional CRM software vendors with flexible, on-demand software services which it claims avoids hefty up-front costs of installation and maintenance.

The company’s shares have swung from $12.70 to up to $25.15 over a 52 week range. Yesterday the company’s stock was down 0.8% at $19.09 during mid-afternoon trading on Nasdaq.